Hi, thanks for all the help and excuse my late reply!

I just tested it with different settings and it looks like it is a combination of File Shield and Mail Shield. Disabling only one still causes problems.
When both are inactive, I am able to create screenshots with no problems.

I tested taking screenshots with an external tool (lightshot) with windows feature (win+print) and with normal printscr (clipboard).

Again, It always creates a file, but the problematic screenshots are either wrong (generic game screen/default background) or the screen after I alt+tabed back to destop.

Edit: I just did a test with the lightshot app closed, still problems with avast active. Testing Fortnite the Game atm.